Garden Talk: March 25, 2010

From NGA Editors

Non-Invasive Spirea

Japanese spirea (Spiraea japonica) is an attractive and widely used landscape shrub. But like some other garden staples such as barberry, burning bush and Norway maple, it can be invasive in areas of the eastern United States, crowding out native plants and disrupting ecosystems.

But ecologically responsible gardeners may not need to say goodbye to this useful plant entirely. Recent research at Montana State University has identified three sterile cultivars of Japanese spirea, ones that do not set seed and therefore cant spread and become a threat to native vegetation. Crispa is a 2-3 tall shrub with deep pink flowers and twisted crinkled foliage; Darts Red has deep,carmine-red flowers and pinkish-red new growth on a 2-3 tall shrub; Neon Flash is of similar size, with bright neon-red flowers that are produced over a long period. (You may see these listed as Spiraea x bumalda cultivars, instead of S. japonica).

Color in the Vegetable Garden

Planting flowers in among your vegetables certainly adds color to the food garden, but its not the only way to liven things up. Why not try planting some colorful vegetables to delight the eye as well as the taste buds? Burpee Seeds has introduced several new varieties that will add spice to your garden and table with their vibrant colors.

The Tye-Dye tomato (78 days) is a bicolor hybrid with an unusual marbling of red and gold. It delivers the great flavor of heirloom varieties such as Big Rainbow, but with bigger yields, consistent form and better disease resistance. The fruits on this indeterminate variety are sweet and mild.

With fruits as large as 12 ounces, Orange Wellington tomatoes (75 days) add a burst of orange to the gardens green. Borne on indeterminate vines, these heavyweights are meaty and nearly seedless, ripening in mid to late summer.

If tomatoes arent your thing, how about cauliflower instead? Colored Mix (55 days) produces heads of purple, green and yellowish-orange along with the more familiar white. This variety is loaded with Vitamin A and is perfect for making a rainbow salad.

Trouble-free Zinnias

Most gardeners love zinnias, with their bright blossoms in all the colors of the rainbow, save blue. There are tall- and short-growing varieties, ones with single or double blossoms- some are even bicolored. But many share a susceptibility to powdery mildew, a fungal disease that covers the leaves with an unsightly coating of grayish-white.

So we are always happy to learn of new varieties that show resistance to this problem. Zahara Starlight Rose is one such zinnia, with delightful single, rose and white bicolor flowers on a 12 to 14-inch tall plant. Not only is it resistant to mildew and leaf spot, it is heat and drought tolerant as well. Its a great choice for color all season long in the flower garden or in a container. Bred by Pan-American Seeds, Zahara Starlight Rose is a 2010 All-America Selections Bedding Plant Award winner.

ÂPrairie DreamÂ Paper Birch

With its white, peeling bark and graceful form, the paper birch is one of the most striking additions to the garden. Unfortunately, in landscape settings it is often short-lived and prone to problems. The bronze birch borer preys on trees that are weakened by environmental conditions, causing dieback starting in the crown of the tree and often leading to its death.

Fortunately for gardeners, Dale Herman, research horticulturist at North Dakota State University, has spent years working to develop woody plants that are hardy in the Northern Plains. One of his recent releases is Betula papyrifera Varden, known in the nursery trade as the Prairie Dream Paper Birch. Hardy to Zone 3, this new cultivar is more tolerant of stresses such as dry soil, winter cold and variable soil pH and has shown a high resistance to the bronze birch borer. With its distinctive bark and dark green leaves that change to golden yellow in the fall, Prairie Dream can add a trouble-free grace note to many gardens. Look for it at your local nursery or garden center; it is also available from mail-order sources.